netdev - Re: use-after-free in sock_wake

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87two93ig8.fsf@doppelsaurus.mobileactivedefense.com>
Date:	Wed, 25 Nov 2015 20:57:59 +0000
From:	Rainer Weikusat <rweikusat@...ileactivedefense.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Rainer Weikusat <rweikusat@...ileactivedefense.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Benjamin LaHaise <bcrl@...ck.org>,
	"David S. Miller" <davem@...emloft.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Ying Xue <ying.xue@...driver.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: use-after-free in sock_wake_async

Eric Dumazet <eric.dumazet@...il.com> writes:
> On Wed, 2015-11-25 at 11:50 -0800, Eric Dumazet wrote:
>
>> >                 other->sk_data_ready(other);
>> > +               unix_state_unlock(other);
>
>
> Also, problem with such construct is that we wakeup a thread that will
> block on the lock we hold.
>
> Beauty of sk_data_ready() is to call it once we hold no lock any more,
> to enable another cpu to immediately proceed.
>
> In this case, 'other' can not disappear, so it should be safe.

I do agree that keeping the ->sk_data_ready outside of the lock will
very likely have performance advantages. That's just something I
wouldn't have undertaken because I'd be reluctant to make a fairly
complicated change to a lot of code in order to improve performance
unless performance was actually found to be lacking and because it would
step onto to many different people's turf.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html